The term wear part is nowadays widely used within the trade as a general designation of all types of more or less easily replaceable wear protectors and teeth used on soil working implements and tools such as buckets, shredders, cutters, etc. on excavators etc. As a rule, a wear parts system consists of adapters attached to the tool concerned with a greater or lesser degree or permancency and one or a plurality of removable front parts, mechanically attached to each and every one of these adapters, the said front parts being the wear parts proper in the form of teeth, cutting edges etc. The ease with which a wear part of this kind is interchangeable varies with the amount of wear to which it can be expected to be exposed. The teeth protruding in front of the tools are particularly exposed to very heavy wear. These, or their outermost tips, to the extent that these are demountable, are therefore nowadays secured in their adapters by means of an easily removable locking element. Changing a damaged tooth is therefore usually done in a matter of a minute or so. The previously mentioned adapters are often welded to or at the front edge of the tool but they can also be mounted with bolts, wedges or by some other means.
Several different wear parts systems are now available on the market but none of them is completely perfect. The main fault with the majority of these systems is that success has not being achieved in mastering the play that which is mechanically secured in the adapter. As a rule, moreover, this play increases in magnitude with the passage of time and cannot be eliminated by a simple replacement of the wear part, since the contact surfaces of the adapter are gradually worn down because the wear part proper mountd therein moves in the adapters as work is being carried out. Hitherto, it has been economically unfeasible to manufacture wear part system components with such fine tolerances that no initial play occurs since this would have required machining the contact surfaces to narrow tolerances. Wear parts are mass-produced goods which, in order to be sold at competitive prices, must be able to be cast or forged directly to their final dimensions without any subsequent chip-forming machining, with the exception of normal burring operations.
Although wear parts subject to play give rise to strikingly increased wear in the vast majority of earth-working tool types, the wear caused by play is nevertheless decidedly the most in the case of rotary dredging cutters or suction dredging cutters. These are used for bottom work, mainly in coral and limestone or otheer softr species of rock. The actual tool consists of a rotary front portion formed by a plurality of toothed spirally twisted vanes disposed at a certain distance from each other which together form a very large drill bit. This drill bit is subsequently rotated with the teeth of the vanes in direct engagement with the bottom rock which is to be worked, at the same time as water is continuously sucked in between the rotating vanes and removed from the point of work. By this means, continuous disposal of broken rock and other bottom sediment is accomplished. The wear parts for such earth-working tools are exposed to extremely heavy wear in their points of attachment on account of the vibrations in the tool and because the tool constantly works in a slurry of sand, clay and/or other abrasive particles. The object of the present invention is to offer a solution to this problem, primarily intended for such dredging cutters but also applicable to every other place where there is a need for wear parts which are seated entirely without play, cannot be loosened by vibrations and are nevertheless very easy to replace.